The present invention relates generally to a method of ablating a hole in a hard, non-metallic substrate, particularly including glass and ceramics. More specifically, the subject invention relates to ablating a hole in a hard, non-metallic substrate using at least one laser.
Drilling or ablating a hole into a hard, non-metallic substrate, such as, for example, glass has proven to be difficult and impractical in a production environmental Prior an efforts to drill holes in a hard non-metallic substrate have utilized diamond tipped drill bits. In order to drill a hole entirely through a hard, non-metallic substrate 24 without causing the edge around the hole to chip, the hole must be drilled, generally, simultaneously from two sides of the substrate. Therefore, two drill bits must be aligned precisely along the same drilling axis. Absent a precise alignment, the hole will not be property formed, and the substrate could be irreparably damaged.
A further difficulty of using opposing drill bits on two sides of the substrate is the probability of damaging the drill bits should contact be made between the two drill bits while drilling the hole. Generally, one drill will be withdrawn from the hole prior to the other drill being engaged with this substrate. However, due to production variability and the small distance between the opposing drill bits, a high probability exists hat the drill bits will make contact and the article being drilled is generally destroyed. If the drill bits become damaged, new drill bits must be installed, which is known to take several hours.
A still further drawback of using drill bits to form a hole in a hard, non-metallic substrate is the inability to form holes having various shapes. It is desirable in many industrial applications to form a hole in a hard, non-metallic substrate that has a shape other than circular, such as, for example, oval, square or other polygonal shape. Given the operational limitations of a diamond tipped drill bit, only circular holes may be drilled in a substrate.
Many glass products require holes that are presently formed by diamond tipped drill bits. These include patio furniture, tempered automotive glass, glass, mirrored electrical and outlet covers. Eye glass lenses are shaped with diamond tipped drill bits. Even glass shower doors require notches to provide space to attach hinges. Forming some of these holes is known to take upwards of 45 minutes. Further, patio furniture does not always present a smooth surface to initiate drilling, which has resulted in production problems.
Lasers have been introduced to cut and etch glass substrates recently to overcome the problems associated with diamond tipped drill bits, but with limited success. U.S. Pat. No. 6,204,472 discloses a method of cutting a hollow glass article using a CO2 laser. The laser forms an incision channel in the glass substrate by vaporizing the glass. However, the depth of the channel is limited and a secondary operation is necessary to separate the hollow glass article at the channel. More specifically, the glass is heated with burners and separated with a percussion tool.
U.S. Pat. No. 5,902,368 discloses severing thin-walled glass substrates using a CO2 laser to heat a particular area of the glass substrate forming a severance point. The glass substrate is then stretched and separated at the heated separation point. However, because the focal point of the laser is not adjustable relative to the glass substrate, the thickness of the glass substrate can be no more than about 0.2 mm.
U.S. Pat. No. 4,441,008 discloses a method of drilling an ultrafine hole through a glass substrate. A CO2 laser is used to drill a hole by establishing a stationary focal point of the laser 0.02 to 0.08 inches below one surface of the glass. The laser is pulsed three to five times to form the hole in the glass substrate. In order to prevent cracking of the glass substrate, the glass substrate is heated to a temperature of between 500° and 1,040° F. prior to activating the laser.
None of the prior art discussed above discloses a method of drilling holes in glass substrates that is practical and cost efficient in a production environment. The underlying drawback of each of these laser devices is the inability to change the focal point of the laser relative to the glass substrate. Therefore, additional steps are necessarily added to the process in order to prevent the substrate from being damaged by the laser. Accordingly, it would be desirable to provide a laser device and ablating method that would enable ablating a hole into a hard, non-metallic substrate by moving the focal point of the laser relative to the depth of the substrate.